Commit ba7c2be1 authored by Clemens Ladisch's avatar Clemens Ladisch
Browse files

ALSA: usb-audio: detect implicit feedback on Roland devices 



All the Roland/Edirol/BOSS USB audio devices that need implicit feedback
show this unambiguously in their descriptors, so it might be a good idea
to let the driver detect this.

This should make playback work correctly (at least with Jack) with the
following devices:
- BOSS GT-100
- BOSS JS-8 Jam Station
- Edirol M-16DX
- Roland GAIA SH-01

Signed-off-by: default avatarClemens Ladisch <clemens@ladisch.de>
parent 8f898e92

sound/usb/pcm.c

+41 −0
Original line number Diff line number Diff line
@@ -298,6 +298,35 @@ static int deactivate_endpoints(struct snd_usb_substream *subs) 
	return 0;

}



static int search_roland_implicit_fb(struct usb_device *dev, int ifnum,

				     unsigned int altsetting,

				     struct usb_host_interface **alts,

				     unsigned int *ep)

{

	struct usb_interface *iface;

	struct usb_interface_descriptor *altsd;

	struct usb_endpoint_descriptor *epd;



	iface = usb_ifnum_to_if(dev, ifnum);

	if (!iface || iface->num_altsetting < altsetting + 1)

		return -ENOENT;

	*alts = &iface->altsetting[altsetting];

	altsd = get_iface_desc(*alts);

	if (altsd->bAlternateSetting != altsetting ||

	    altsd->bInterfaceClass != USB_CLASS_VENDOR_SPEC ||

	    (altsd->bInterfaceSubClass != 2 &&

	     altsd->bInterfaceProtocol != 2   ) ||

	    altsd->bNumEndpoints < 1)

		return -ENOENT;

	epd = get_endpoint(*alts, 0);

	if (!usb_endpoint_is_isoc_in(epd) ||

	    (epd->bmAttributes & USB_ENDPOINT_USAGE_MASK) !=

					USB_ENDPOINT_USAGE_IMPLICIT_FB)

		return -ENOENT;

	*ep = epd->bEndpointAddress;

	return 0;

}



/*

 * find a matching format and set up the interface

 */
@@ -393,6 +422,18 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt) 
			goto add_sync_ep;

		}

	}

	if (is_playback &&

	    attr == USB_ENDPOINT_SYNC_ASYNC &&

	    altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC &&

	    altsd->bInterfaceProtocol == 2 &&

	    altsd->bNumEndpoints == 1 &&

	    USB_ID_VENDOR(subs->stream->chip->usb_id) == 0x0582 /* Roland */ &&

	    search_roland_implicit_fb(dev, altsd->bInterfaceNumber + 1,

				      altsd->bAlternateSetting,

				      &alts, &ep) >= 0) {

		implicit_fb = 1;

		goto add_sync_ep;

	}



	if (((is_playback && attr == USB_ENDPOINT_SYNC_ASYNC) ||

	     (!is_playback && attr == USB_ENDPOINT_SYNC_ADAPTIVE)) &&

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